In order to secure soft tissue, for example a ligament or a tendon, to a bone, it is known to introduce a bore, in particular in the form of a blind hole, into the bone and to insert a bone anchor into the bore. The bone anchor remains in the bone and provides a firm hold for a thread, a band or another connecting means with which the soft tissue is secured on the bone. In this way, for example in the event of an injury, ruptured soft tissue parts can be fixed at the incision site. Known bone anchors of this kind, designed as implants, often use an interference fit or large thread flanks in order to achieve a secure hold in the bone. Particularly in the case of press-fit implants, for example an impaction anchor with ribs, or in the case of interference screws, the external diameter of the implant is greater than the diameter of the bore. To achieve the secure hold, a force is applied from the inside to the wall of the bore, which in extreme cases can lead to a fracture of the bone.
It is also known to generate an undercut in a bore introduced into a bone, particularly in a blind hole, thereby creating a cavity in which a bone anchor can be held with a form fit. U.S. Pat. No. 5,928,239 discloses a surgical device for generating a cavity in a bone, which device has an elongate shaft and a cutting tip, which is arranged with a freely rotatable hinge on the tip of the shaft. By rotation of the shaft at a sufficient speed, the cutting tip is deflected to a pivoted position and thereby generates a cavity, of which the radius is defined by the length of the cutting tip. From EP 2 098 177 A1, a surgical instrument with a shaft is known in which a cutting element is secured on the distal end of the shaft, which cutting element can be brought from a position in alignment with the longitudinal axis of the shaft to a deflected position. According to WO 2007/047065 A1, a surgical instrument for generating a cavity has a lateral window at the distal end of a shaft, wherein a blade, pick or tip can be brought from a position inside the shaft to a position at least partially protruding from the window. However, these known tools have a relatively complex structure and are not optimal in terms of their handling during use, particularly in the case of bores with small diameters.
The international patent application WO 2014/089198 A1, unpublished at the priority date of the invention, discloses a cannulated retrograde reamer with a drill bit, an elongate outer tubular shaft, and one or more cutting elements. By movement of the outer tubular shaft in the direction of the drill bit, the cutting elements come up against an abutment of the drill bit and rotate outward. The reamer can be used with a guide wire.